A fermentation production process of chemicals using sugar as a raw material is used in various industrial raw material production. As the sugar to be a fermentation raw material, materials derived from food raw materials such as sugarcane, starch, and sugar beets are now industrially used. From the viewpoint of a steep increase in the price of the food raw materials due to an increase in future world population or ethical issue that the industrial raw material use competes against food use, establishment of a process in which a sugar solution is more efficiently produced from a reusable nonfood resource, that is, cellulose-containing biomass or a process in which the obtained sugar solution is efficiently converted into industrial raw materials as a fermentation raw material is a future problem.
The cellulose-containing biomass is mainly made of lignin that is an aromatic polymer and cellulose and hemicellulose that are polymers of monosaccharides. The sugar solution is generally obtained by using a method according to an enzymatic saccharification reaction. The method according to an enzymatic saccharification reaction, for example, includes the steps of carrying out pretreatment of lignin-protected cellulose or hemicellulose by mechanical treatment such as grinding treatment or thermochemical treatment using high temperature and high pressure water, dilutes sulfuric acid, and ammonia; removing cellulose or hemicellulose from lignin (refer to Japanese Patent Application Laid-open No. 2009-183805 and Japanese Translation of PCT Application No. 2008-535523) to obtain pretreated biomass; thereafter mixing a saccharification enzyme with the pretreated biomass; and hydrolyzing the cellulose or hemicellulose obtained by removal from the lignin with the saccharification enzyme to produce monosaccharides.
Production of the monosaccharides from the cellulose-containing biomass using the enzymatic saccharification reaction has a problem in facilities. First, efficiency of the saccharification derived from the cellulose-containing biomass using the saccharification enzyme (performance of the saccharification enzyme) is lower than that of the saccharification derived from starch and thus one day to several days are required for the hydrolysis reaction. Consequently, the residence time of the cellulose-containing biomass in the reaction equipment becomes longer and thus the facility cost becomes higher. Second, the saccharification reaction in high concentration of the cellulose-containing biomass may have such troubles that a stirrer does not rotate and a liquid (a slurry liquid) in a slurry state cannot be transferred. Consequently, the concentration of the cellulose-containing biomass at the time of enzymatic saccharification reaction has limitations and thus the concentration of the obtained sugar solution becomes low.
Various methods have been developed to solve the above problems in the facilities for the enzymatic saccharification reaction using the cellulose-containing biomass. Examples of the methods include a method of intermittently feeding pretreated biomass (for example, refer to Japanese Patent Application Laid-open No. 2001-238690 and Japanese Translation of PCT Application No. 2010-536375), a method of accelerating a reaction by once carrying out solid-liquid separation and mixing the residue and water (for example, refer to Japanese Patent Application Laid-open No. 2011-19483), a method of carrying out the saccharification reaction again after the grinding treatment of the residue (for example, refer to Japanese Patent Application Laid-open No. 2011-41493), and a method of adding water to pretreated biomass to form slurry (for example, refer to Japanese Patent No. 4764527).
However, although the method of intermittently feeding the pretreated biomass as described in JP '690 and JP '375 can increase sugar concentration at the time of saccharification, efficiency of the saccharification decreases because the reaction times of the saccharification enzyme of the pretreated biomasses fed in advance and the pretreated biomasses fed afterward are different.
The methods described in JP '483 and JP '493 suppress equilibrium reaction inhibition caused by the generated sugar to shorten the saccharification reaction time. However, the amount of added water is larger than the amount of water that is usually added. The method described in JP '493 requires additional energy to grind the material.
JP '527 discloses a method of reducing thermal over-decomposition of biomass by providing a slurrying tank. However, the liquid cannot be transferred without reducing the solid content concentration. As a result, the sugar concentration may decrease.
In the methods described above, problems remain in that the cellulose-containing biomass is difficult to saccharify in a high concentration or the facility cost becomes higher due to the longer reaction time.
In view of the above problems, it could be helpful to provide a device that produces a sugar solution that can effectively produce a sugar solution in a high concentration and a method of producing a sugar solution.